Minimizing irrigation water losses

Increasing and competing demands for freshwater â€' for drinking, agricultural, urban and industrial uses â€' are placing increased pressure on global water resources.

Minimizing irrigation
water losses

Increasing
and competing demands for freshwater â€' for drinking, agricultural, urban and
industrial uses â€' are placing increased pressure on global water resources.
Irrigation of crops is the main user of freshwater resources in most developing
countries and in Australia. Growing populations and associated urbanisation
are, however, accelerating water consumption. ACIAR is supporting research on
more efficient irrigation in developing countries, to relieve some of this
pressure.

The
use of water for agricultural irrigation dates back to the ancient
civilisations of Egypt, Mesopotamia and China. These ancient civilisations
organised their cultures around irrigation resulting in few competing demands
for water.

Today
rapid population growth has increased urbanisation, particularly in developing
countries. More mouths mean more water for drinking; greater population
densities require more water for sanitation; while industrialisation has raised
the thirst for water from manufacturing and commercial sectors. Environmental
flows to replenish depleted water resources are being utilised in a number of
developed countries, and in some developing countries.

The
resulting total of these demands is far greater pressure on water resources and
water users. Laguna de Bay in the Philippines provides an excellent example of
these competing needs. It is comprised of three bays that combine into the largest
freshwater body in the Philippines. The Eastern Bay is planned as a freshwater

resource
for the expanding needs, and area, of eastern bayâ€˜s is
themainPagsanjanwaterRiver,part ofsourcethePagsanjanLumban catchment. Most of

the
water arises from runoff from agricultural land with potential for
contamination by eroded soil and associated nutrients.

Utilising
this resource for competing needs, in a sustainable manner, is the challenge
faced in the Philippines, and mirrored elsewhere. ACIAR is addressing these
challenges through projects, including one addressing the need to limit inflows
of sediments and nutrients in eastern Laguna de Bay, that:introduce greater
efficiency of agricultural water use, including optimising distribution within
irrigation systems, manage and reduce impacts from water use, such as salinity
and runoff and transport of agrochemicals, and

explore and develop
alternatives to traditional
approaches, both at
the

Nowhere is water under
greater demand than China. Irrigated rice production is vital in China and is
one of the largest users of available water. Traditional rice growing included
maintaining continuous flooding of paddy fields using a large amount of water
to achieve high yields. Without these yields China would struggle to produce
enough rice. The introduction of new irrigation methods for rice based on
alternate wetting and drying of soils instead of continuous flooding have been
trialled. Results showed less water is used while maintaining high yields.
Already 1.5 million hectares of land in China is under the wettingdrying
technique, and this is now being trialled in Sri Lanka and the Philippines.

A
separate project on Chinaâ€˜s Zhanghe Irrigatio to ordering water. To reduce
their water bills farmers tended to wait for rain, but if this did not arrive
most

ordered
water in response to visible crop stresses. This often occurred at the same
time, creating a peak demand period during which the system was unable to cope.
Water saving irrigation technologies and changes to water delivery procedures
helped maintain crop yields with reduced water usage.

Extensive
irrigation can also contribute to other problems, notably rises in shallow
groundwater and through this salinisation. Chinaâ€˜s Yinchuan Plain is ex between
domestic and agricultural uses causes water shortages, while irrigation is
accelerating the rise in groundwater. This rise is also mobilising soilbound
salt, resulting in salinisation.

Using
hydrological models digital maps of salinity hazard were developed. These have
been used to determine high risk areas to introduce techniques such as deep
open drains that reduce the shallow water table. Using some groundwater in
conjunction with irrigated water and furrow irrigation reduces by 30 per cent
water losses that occur in traditional irrigation.

Groundwater
as a potential irrigation supplement for growing dryseason vegetable crops is
being examined in the Philippines. Overexploitation of groundwater is a threat
to longterm agricultural production in areas

relying
on rainfall. Sustainable groundwater extr dryseason.

An
ACIAR project has examined more efficient water distribution at the basin level
of the Yellow River, focusing on irrigation demands within the context of
government water and agricultural policies. More efficient water allocation can
be achieved by establishing equitable institutional arrangements on a
networkwide basis. Similar projects are underway in India and Vietnam.

Indiaâ€˜sBasinKrishnasourceofwater
for agriculture, industrial and domestic uses in Andhra Pradesh, Karnataka and
Maharashtra. ACIAR is supporting decision making in the affected states by
assisting the development of an integrated framework to formulate and evaluate
allocation strategies. Key trends and figures on water flows are being used in
economic and scenario modelling.

Three
other Indian states of the East India Plateau with a combined population of 27
million rely on rainfall during the monsoon for crop productivity. Watershed
management and the sustainable use of water, such as through water harvesting,
are priorities. ACIAR is working to improve these aspects of water management.
A similarthemed project for the Philippines Inabanga watershed, on Bohol
Island, has recommended management options for the area.

Raised crop beds
have been trialledwheat cropping India,systems P

rely on irrigation
water. Trials of the use of permanent raised beds on which crops are planted
have lowered

water consumption for
irrigation. Raised beds have also been trialled for wheatmaize rotations in
Pakistan, for vegetables on heavy clay soils in Indonesia, and for wheat in
China. In each country increased yields and lower irrigation water use have
been achieved.

Less
water use also reduces opportunities for runoff. In the Philippines, China and
Thailand pesticide contamination of water resources has potential to cause
health and environmental problems. An ACIARWorld Vision project has reduced
chemical runoff and contamination of nearby water sources, with the farmers
involved earning a price premium for selling chemicalfree vegetables.

A
risk based approach to the management of pesticides was introduced in parts of
the Philippines to minimise offsite flow of chemicals. Simple techniques at the
field level and equipping catchment managers in integrated pest management have
reduced the reliance on pesticides. In China production and handling systems
are being examined to determine risk factors leading to vegetable
contamination. The focus is on efficient decontamination strategies and introducing
improved postharvest practices.